The idea of fractional calculus has been known since the notion of fractional derivative was firstly introduced by Leibniz in a letter dated 30th September, 1695, where half-order derivative was mentioned. Since then it was subsequently developed by Euler, Lagrange, Laplace, Fourier, Abel, Liouville, Riemann, Heaviside, Caputo along with many others [1]}. Generally, fractional calculus deals with the study of fractional order integral and derivative operators over real or complex domains and their applications [2]}. Specially it is a generalization of classical differential and integral calculus of integer order to arbitrary order. In recent times, fractional order derivatives and fractional order differential equations have been applied in several fields of science and engineering [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, however, initially it was treated as a topic of interest of pure mathematicians only [11]}. The reason is two-fold. First, fractional derivatives have an additional degree of freedom over its integer order counterpart due to the additional parameter that represents its order and more suitable for those systems having higher order dynamics and complex nonlinear phenomena [12]}, [13]}. Secondly and more importantly, fractional order derivatives not only depend on the local conditions but also on the history of the function [14]} and, therefore, fractional derivatives have become an efficient tool for those systems, where the consideration of memory or hereditary properties of the function is essential to represent the system, e.g., in the case of biological systems. In the last two decades, fractional order calculus has found its many applications in biological sciences [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, [22]}, [23]}.
